claims depot shelf
The Hubble Tension
Formal claims (Lean)
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The paper's central claim is that the weak-field gravitational force $F = -GMm/r^2 + \Lambda c^2 mr/3$, obtained from the theorem that only this force keeps the exterior field of a sphere equivalent to a point mass, changes cosmic structure formation in two linked ways. In the kinetic description, the stationary Vlasov-Poisson system with this force reduces to a Hammerstein integral equation for t
Stated claims
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The central discovery is that the level of evidence for dynamical dark energy, measured by fitting the CPL parametrization $w(a)=w_0+w_a(1-a)$ to BAO and uncalibrated supernova data, is not a single number but a field over the early-universe parameters ($H_0 r_d,\Omega_m$). Only the product $H_0 r_d$ and the expansion shape $E(z)$ are accessible to these late-time probes, so the same data can support 'cosmological constant' or 'dynamical dark energy' depending on where the early universe places the model. The CMB angular scale provides an almost model-independent ridge in this plane, and the minimum of the dynamical-dark-energy preference, the 'nexus,' sits on that ridge without having used CMB data. Early-universe solutions to the Hubble tension, which move the joint fit to higher $H_0 r_d$ and lower $\Omega_m$, push the fit toward that nexus and reduce the significance from about 2.5σ to 1.3σ, making the apparent preference depend on the assumed early cosmology. A fourth-order Chebyshev reconstruction of the dark energy density confirms the same weakening near the nexus.
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Using the M25 peculiar velocity reconstruction to correct the redshifts of the six megamaser galaxies gives a best-fit Hubble constant $H_0 = 68.7 \pm 2$ km/s/Mpc when the velocity uncertainty $\sigma_v$ is treated as a free parameter and marginalized over with a prior limit $\sigma_v \le 150$ km/s. The probability that the true $H_0$ is as large as the distance-ladder value of $73.5$ km/s/Mpc is only $2.9\%$ (rising to $4.9\%$ if the prior limit is widened to $200$ km/s). This is the opposite of the original P20 analysis, which modeled peculiar velocities as Gaussian noise and obtained $H_0$ close to the distance ladder; the shift arises because all six galaxies have positive M25 peculiar velocities, which systematically lowers the corrected redshifts and therefore lowers $H_0$. The paper argues that previous estimates were biased high by peculiar velocities, and that the more accurate, higher-resolution M25 reconstruction removes much of that bias.
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The central claim is that the observed gravitational-wave strain from a compact binary merger contains two separable cosmological observables: the luminosity distance dL from the oscillatory part of the signal, and the integrated cosmological memory (ICM) offset from the post-merger step. The ICM amplitude follows N+ = h⊕/(3 E^{2/3}(z0)) ∫0^{z0} (1+z)/E^{4/3}(z) dz, where E(z)=H(z)/H0; because this integral weights the expansion history differently than dL does, the pair (dL, R=N+/h⊕) lands on a unique point in the R–dL plane for each expansion history, fixing both distance and redshift for a single event. The authors demonstrate the extraction in simulation: standard Bayesian parameter esti
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The paper claims that linear matter clustering at scales near k=0.1 h/Mpc is plausibly suppressed relative to the GR/ΛCDM prediction, with an effective gravitational coupling Geff=G/(1+Aξ) where ξ∝(1+z)/k². Using a joint MCMC analysis of 35 uncorrelated fσ8 measurements, cosmic chronometer H(z) data, Pantheon+ supernovae, and CMB power spectra and lensing, the inferred amplitude A=4425±2000 (equivalently B=0.36+0.14−0.12) gives a 2.2σ preference for a non-zero scale-dependent term. The suppression is stronger during the matter-dominated era than in the dark-energy-dominated epoch, and the derived S8=0.831±0.011 matches the CMB-inferred value without exacerbating either the S8 or H0 tensions.
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On the paper's own terms, the central discovery is a reframing: the 'Hubble tension' between local distance measurements and the CMB is not primarily a conflict over the expansion rate H0 but a conflict over the standardized peak absolute magnitude M_B of Type Ia supernovae. The first two rungs of the distance ladder measure M_B = -19.204 ± 0.030 from 17 nearby Cepheid-calibrated host galaxies, with no cosmological assumption. The same supernova population, inserted into CMB-constrained standard cosmology and fit over redshifts 0.04 to 1, demands M_B = -19.430 ± 0.013. The 0.23-magnitude gap is about 7 sigma and survives any smooth change in the late-time expansion history; fitting the magni
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For an axisymmetric Bianchi type I background with freely decaying shear and isotropic pressure, the fractional luminosity-distance quadrupole AD(z) is fully determined through relative order z^2 by the present directional expansion contrast BH0 and the background deceleration and jerk parameters: AD(z) = -BH0 + (2q0 - 1) BH0 z / 2 + (5 - q0 - 18q0^2 + 6j0) BH0 z^2 / 12 + O(z^3, BH0^2). The formula separates two physical contributions: the direction-dependent redshift–affine-parameter mapping, which dominates at low redshift, and the Jacobi-focusing term, which first enters at order z^2. In the minimal model the direct quadrupolar Ricci focusing vanishes, while isotropic Ricci focusing contr
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The authors establish, using analytic arguments, that a mass-varying dark matter model with one bare potential V(φ) and one coupling scale M can generate an early dark-energy-like peak near matter-radiation equality and a late-time apparent phantom crossing near matter-dark-energy equality. The early peak's amplitude is set by the ratio m(φi)/m(φ0) − 1, its timing by the curvature of m(φ), and the late-time crossing is driven by the bare potential pushing the field at low redshift—exponential potentials doing this most naturally. Since both effects stem from the same mass function m(φ), the same range of M controls both, and the timing tracks the background evolution rather than separate ene
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The paper's central claim is that quantum corrections derived from Weyl-Wigner phase-space mechanics can dissolve the Hubble tension. Starting from a minisuperspace action and the Wheeler-DeWitt equation, it identifies the classical potential as a sum of powers of the scale factor and computes the effective quantum potential induced by a sinusoidal Wigner function W(x,k;τ)=g(x;τ) sin(μ k x). Each power x^{−κ} in the potential is rescaled by a factor b_κ(μ)=2κa_κ μ^{−κ}[(2−μ)^{−κ}−(2+μ)^{−κ}], which modifies the matter and radiation energy densities in the Friedmann equation. The result is an effective Hubble parameter h̃(x) that sits at about 0.673 at last scattering and rises smoothly to ab
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The central claim is that the entropy-area relation with a scale-dependent exponent Δ(x)=Δ0+Δ1/ln x, where x=(H1/H)^2, when fed into the gravity-thermodynamics first law on the apparent horizon, yields an exact analytic Hubble rate H(z). Combined fits to Hubble-rate measurements, type Ia supernova distances, baryon acoustic oscillations, and CMB shift parameters give H0 = 69.27^+0.62_-0.65 km/s/Mpc with Δ0 ≈ 2.4×10^-3 and Δ1 ≈ -0.65, implying Δ(0) ≈ 1.09×10^-4. The derived Δ(z) crosses zero at z_tr ≈ 100 (with broad uncertainties), connecting a negative-Δ early phase to a positive-Δ late phase. The model is fully consistent with the data but is not statistically preferred over ΛCDM (ΔBIC ≈ 7
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The central discovery is that a cosmological model in which the Gauss-Bonnet correction to the Wald entropy of the apparent horizon is sourced by the astrophysical history of black-hole formation and mergers fits the combined early- and late-Universe data better than ΛCDM, with the coupling parameter Cn = 0.435^{+0.150}_{-0.132}, a ~3σ phantom-side deviation from zero. The mechanism preserves the standard acoustic scale, leaving the primary CMB nearly unchanged, while the late-time expansion is enhanced enough to shift H0 upward by about 1.3 km/s/Mpc. The cost is a modest rise in S8, and independent growth probes (lensing and redshift-space distortions) are slightly worse-fit than in ΛCDM. T
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Applying the revised Pantheon+ host-mass magnitude corrections to the 52 affected H0DN Hubble-flow rows, with network covariance, redshifts, and velocities held fixed, yields H0 = 73.264 ± 0.806 km s⁻¹ Mpc⁻¹ and a 6.85σ tension with H0^CMB,ΛCDM = 67.24 ± 0.35. Replacing the full Hubble-flow rung or substituting DES-DOVEKIE (first application to a distance ladder) via a constant overlap offset produces values still near 73; neither update resolves the tension.
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The central claim is that the entropic generalized Chaplygin gas — a unified dark fluid with equation of state p = -A/ρ^α, plus an entropy perturbation that drives the effective rest-frame sound speed to zero — is consistent at the background level with the full set of late-Universe distance and growth data, and that its only significant effect is a late-time bending of the distance-redshift relation. The paper argues this deformation moves the joint posterior in (H0, Ωm, S8) almost exclusively along directions controlled by the expansion history: with one supernova calibration it substantially shifts H0 and improves the fit over ΛCDM; with another calibration the two models nearly coincide.
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On the paper's own terms, the central discovery is a negative one: after sorting all proposed explanations by the part of the cosmological inference chain they modify, no model simultaneously preserves the CMB acoustic peak structure, the baryon-acoustic-oscillation standard ruler, the supernova distance-redshift relation, lensing, structure growth, and local absolute calibration. Early-time models like early dark energy can shrink the pre-recombination sound horizon, which is the necessary direction for raising the CMB-inferred H0, but the paper's reference chains show that uncalibrated data keep the early component small (fEDE ≈ 0.02–0.04 with H0 ≈ 67.8–69.4) and only a direct local-H0 cal
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The central discovery is a simple ratio identity: with the CMB acoustic angular scale and the sound horizon fixed, a fractional increase in H0 equals the fractional increase in the dimensionless distance integral I ≡ ∫_0^{z★} dz/E(z). The paper splits I into a low-redshift part I<, directly constrained by data, and a high-redshift part I> that is not, and shows that Gaussian Process reconstructions of E(z) — built only from relative distances, with the BAO normalization marginalized — keep δI_</I_< below about 1.5 percent at 95% confidence for the combination of supernova and BAO data. Accounting for I> with smooth-model estimates yields δH0/H0 ≲ 2.07% (conservative) or ≲ 3.67% (maximally pe
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The paper's central claim is that a vEDE component, which boosts the expansion rate only while deuterium is finishing its burning around T_D ≈ 0.03 MeV, can reconcile the measured primordial deuterium abundance with the higher baryon density inferred from CMB data in early dark energy cosmologies. Quantified as ΔH/H(T_D) = 0.087 +0.036/−0.037, this boost preserves D/H at the high baryon density while barely changing helium-4, reducing the tension from 3.1σ to 0.7σ. The timing of the extra expansion is the key: a constant radiation excess raises helium-4 too efficiently and fails to reconcile the two baryon-density determinations.
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The paper shows that, in a flat ΛCDM cosmology, the constraining power of bright sirens on H0 is concentrated at low redshift when used alone: the luminosity distance becomes increasingly sensitive to Ωm and statistically noisier at higher redshift, so sources beyond z∼1 add little once Ωm is left free. This is quantified by a binned and a cumulative redshift analysis, both of which show a plateau in the H0 uncertainty around z∼1. When a mock BAO measurement is added, the H0–Ωm degeneracy is broken, the informative redshift range extends to z∼2, and far fewer events are required: roughly 20 bright sirens for σ_H0≈1 km/s/Mpc and 15 for σ_H0≈2 km/s/Mpc, compared with about 90 and 45 in the bri
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In a Planck-calibrated flat LambdaCDM background, matching the SH0ES measurement of H0 through a void-induced local expansion excess requires a present-day enclosed density contrast of about -0.44, roughly 50% deeper than the KBC benchmark of -0.3. A KBC-like void lowers the statistical tension from above 5 sigma to about 2 sigma, and the tension remains below 3 sigma only for voids with depths between about -0.64 and -0.22. Varying the dark-energy equation-of-state parameters w0 and wa over broad CPL ranges, including regions motivated by recent DES and DESI analyses, shifts the required depth by less than a percent, so dynamical dark energy cannot rescue a shallow KBC-like void. The paper
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On the paper's own terms, the central discovery is that a natural dark-matter–dark-energy interaction arises when the complex scalar potential is expanded near its maximum, and that this interaction makes the effective Hubble constant decrease with redshift in a way that matches the binned Pantheon supernova data. The key result is the closed-form solution ϵa = ϵa0 (1+z)^3 e^{-2δρ/σ0}, which shows the axion (dark matter) energy density is exponentially suppressed as the modulus displacement δρ grows; this suppression is what bends H0(z) downward. The best-fit value Δ = 0.00964 ± 0.00457 quantifies the effect, and the paper reports its statistical performance is between the empirical power-la
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Central claim: ~10^-18 solar-mass PBHs at 10^-3 of the dark matter density delay recombination by Δz≈64, translating to an 8.9% rise in the CMB-inferred H0. A fully evaporated PBH heats its surrounding gas independently of mass; abundance above 10^-2 would fully reionise at recombination. The 8.9% is nominal: grey-body factors and full CMB fitting lower the required fraction, leaving the tension not fully relieved.
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The paper's central claim is that the generalized mass-to-horizon entropy class, despite its additional parameters, is observationally forced back to standard Bekenstein–Hawking thermodynamics: the entropy exponent satisfies |m−1| ≲ 10⁻⁴ when the MHR coupling is fixed and ≲10⁻³ when the coupling is free, and the derived coupling and entanglement amplitude deviate from their ΛCDM values only along degeneracy directions. It further claims that the apparent resolution of the Hubble tension is an artifact: adding parameters absorbs the CMB–SH0ES discrepancy, pushing h to 0.70–0.71, but the Bayesian log-evidence is negative for every extension in every dataset combination (−16 ≲ Δ ln Z ≲ −1). The
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The central claim: apparent phantom crossing can arise from a well-defined interacting dark sector, not a fundamental phantom field. In the DADB model, the dark QCD axion's effective potential depends on dark-baryon density; the baryon mass varies as the axion rolls, falling before recombination and rising afterwards. This non-monotonic mass evolution fits the CMB while producing an apparent phantom crossing over the BAO/supernova epoch. Fitted to CMB, BAO, and recalibrated supernova data, the best model beats ΛCDM by Δχ²=-14.48 with three extra parameters. The same dynamics yields an early-dark-energy component peaking at ~0.8% of total density, too small to resolve the Hubble tension.
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The abstract reads: "the HN c-field dynamics is shown to be encompassed by the GCG equation of state through an equivalent modified scalar field theory." Concretely, Eq. (46) H²(φ)=H²(ϕ)-ċ²/3, together with the derived ρφ and pφ in Eqs. (57) and (60), and the tanh-deformation case with c_s²>0 for all scale factors. If correct, the creation field belongs to a broader scalar-field dark-sector family that can modify the late-time Hubble rate while keeping the effective fluid linearly stable.
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The central claim is that the six-parameter concordance model—with parameters Ωb h², Ωc h², θMC, τ, As, ns—continues to provide an adequate description of all CMB temperature and polarization power spectra through the 2020s. Planck measured seven acoustic peaks and troughs to ℓ ≈ 2500; the EE and TE spectra independently agree with the TT-derived parameters; gravitational lensing is detected at 40σ in temperature; and searches for primordial B-modes have only strengthened the upper bound to r < 0.036. The review regards the absence of any statistically significant departure from this model, apart from the H0 tension, as the summary finding of the past decade.
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On its own terms, the paper's finding is a hierarchy. In the baseline analysis, ΛCDM sits at a 5.4σ (ΔDMAP) tension with the locally calibrated supernova magnitude, and no contender closes the gap completely. The best performers are early-time mechanisms: axion-like early dark energy reaches a residual 2.5σ with −ΔAIC ≈ 23 and log-Bayes ≈ 10.5; early modified gravity, Rock'n'Roll, and NEDE cluster at 2.7–3.1σ. The varying-electron-mass model is the only non-early contender to pass the selection thresholds, at roughly 4σ; radiation and late-time groups stay near or above 4.5σ. Without ACT data, most radiation and recombination models recover to 3–3.5σ, so the preference for early dark energy
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The central claim is that, in a common statistical framework applied to the baseline CMB+BAO+SN dataset, the four early-energy models (axion-like early dark energy, cold NEDE, early modified gravity, and its Rock'n'Roll limit) are the only contenders that both reduce the residual calibration tension to the 2.5–3.6σ level and achieve strong joint-fit support over ΛCDM (−ΔAIC > 10 and ln BF > 3). A localized non-radiative contribution near matter–radiation equality is thus identified as the most effective mechanism, because it shrinks the sound horizon while leaving the detailed high-multipole CMB spectra and the low-redshift distance relation intact. The paper does not claim any model fully r
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In the phenomenological ξ IDE model the combination ξ + 3w_X is negative for every dataset combination examined, corresponding to energy transfer from dark energy to dark matter; the tightest constraint is ξ + 3w_X = −0.035 ± 0.023 (1.52σ from zero) for CMB + DESI DR2 + CC + Union3, so current data supply only a weak indication of a non-zero dark-sector interaction while Bayesian evidence continues to prefer ΛCDM.
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Joint analysis of DESI DR2 BAO with CC, SNIa and CMB distance priors yields H0 = 64.05 ± 0.27 km s^{-1} Mpc^{-1}, Ωm = 0.3264 ± 0.0043 and Ωk = 0.0088 ± 0.0016 (non-flat DGP) or H0 = 63.28 ± 0.25 km s^{-1} Mpc^{-1} and Ωm = 0.3303 ± 0.0036 (flat DGP). Both cases give ΔAIC ≳ 100 relative to ΛCDM, driven by the model’s inability to fit DESI BAO and CMB distance priors at once, and produce a delayed transition to acceleration at zt ≃ 0.41.
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The central result is an equation (Eq. 8) showing that, for a fixed sound-horizon calibration, the Hubble constant is determined entirely by the distance-duality parameter η, the supernova intercept M, and the sound horizon r_d—none of which depend on the late-time expansion history. This means no modification to late-time expansion alone can shift H_0 unless it also breaks distance duality. The paper then shows that the required ~8–10% duality violation is excluded because its two components are independently constrained to sub-percent and percent levels by current BAO, cosmic-chronometer, and CMB-temperature data.
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The heliosphere acts as a coherent, observer-side optical filter: plasma refractive-index gradients across the heliopause produce a weak-lensing flux enhancement δ_helio of order 0.08 for upwind lines of sight at 550 nm, enough to shift the local distance ladder by several percent and thereby contribute 3–8 percent of the Hubble tension once anisotropy and calibration effects are included.
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Angular cross-correlations of distance indicators with galaxy redshift catalogues, analysed jointly in redshift space and in observed-distance space, break the H0–ΔM degeneracy and thereby constrain a constant calibration bias without relying on primary distance-ladder anchors.
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When linear dark-energy perturbations are treated consistently, the smooth error-function ECDM model is fully compatible with current precision CMB, BAO and supernova data and simultaneously lowers the Hubble tension relative to flat ΛCDM.
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Joint strong-lensing constraints on the sign-changeable interaction Q = 3 beta H rho_dm q yield best-fit values Omega_dm0 = 0.253^{+0.018}_{-0.004} and beta = -0.83^{+0.10}_{-0.08}. This large negative beta implies dominant energy flow from dark energy to dark matter, producing a constantly accelerating Universe whose deceleration-parameter zero-crossing occurs at z_t = 2.33 rather than the Lambda-CDM value 0.64.
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With ten years of DUNE exposure the experiment can set 3σ upper bounds on the long-range potential of order 10^{-14} eV in the eμ and eτ sectors, thereby excluding previously unexplored regions of the (mZD, geff) plane down to geff ≲ 10^{-28} at mZD ∼ 10^{-35} eV; the same underlying active–dark mixing simultaneously produces neutrino self-interaction strengths G4 u_eff ∼ 10^9–10^{10} GF that are cosmologically relevant for the Hubble tension.
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With Planck 2018 + DESI DR2 + DESY5, both discrete and continuous unimodular diffusion models identify a transition phase at intermediate cosmic times and yield slight evidence relative to ΛCDM according to ΔDIC (especially when curvature is allowed), while remaining non-decisive on the sign of Δ ho_Λ and not significantly alleviating the H0 tension.
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In two physically motivated k-essence cosmologies the Planck–late-Universe Hubble tension falls from 5.89σ in ΛCDM to 0.14σ (dilaton) and 0.69σ (tachyon) once all late-time probes are combined; the reduction is stable across every independent late-time combination and occurs without dataset-dependent retuning of the k-essence parameters.
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When constrained by late-time H(z), SNe Ia, DESI DR2 BAO, and an RSD growth compilation with free sound horizon, none of the three holographic-inspired models significantly alleviates the Hubble tension. Holographic dark energy is driven to c ≃ 1 (near the de Sitter boundary), agegraphic dark energy to n ≃ 2.8, and Ricci dark energy to γ ≃ 0.53–0.55 with Ωm0 ≃ 0.215–0.219; holographic dark energy is the most balanced of the three, yet current data do not decisively prefer it over ΛCDM.
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Using Planck CMB data together with DESI BAO and multiple supernova catalogues, dynamical dark energy continues to be preferred at similar significance in every extended model examined. Curvature remains consistent with zero, though a 2.2-sigma hint for positive Omega_k is strongly reduced once dynamical dark energy is allowed. Effective neutrino number stays compatible with the standard value while the upper limit on total neutrino mass ranges from 0.06 eV to 0.2 eV depending on the model. No primordial tensor modes are detected and the spectral index shows model dependence that can be partly absorbed by allowing small runnings, yet none of the extensions resolve the Hubble tension.
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Applying YY isochrones to a sample of 247,103 stars with LAMOST spectroscopy and Gaia parallaxes, then restricting to metal-poor alpha-enhanced objects with consistent FLAME ages, produces a final catalog of 155,600 stars within 5 kpc. MCMC reconstruction of the latent age distribution gives an oldest-star age A_star of 13.73^{+0.18}_{-0.15} Gyr. This matches the 13.6 Gyr expected in CMB-calibrated Lambda-CDM under the assumption that the first long-lived stars formed 0.2 Gyr after the Big Bang, thereby casting doubt on pre-recombination solutions to the Hubble tension that imply a cosmic age of only 12.9 plus or minus 0.2 Gyr.
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The f(T,B) model with the chosen power-law ansatz reproduces the observed expansion history, yields an improved AIC score on the CC+PPS combination relative to ΛCDM, exhibits phantom-divide crossing, and produces an H0 value that partially relieves the tension between early- and late-time measurements.
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Moving from ΛCDM to EDE increases the inferred α_s: once the acoustic angular scale θ_s is fixed, EDE increases the diffusion-to-acoustic angular scale ratio θ_d/θ_s, and the shift in α_s compensates this extra damping by increasing small-scale power.
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The exponential infrared f(T) model admits two distinct solution branches. Model I behaves like phantom dark energy and reduces the Hubble tension relative to Lambda CDM but is still disfavoured by the combined dataset. Model II produces a negative-to-positive transition in the effective torsional dark-energy density and is decisively ruled out. This exclusion stems from the interplay between background and perturbation constraints: once distance measurements fix the expansion, the model forces correlated parameter shifts that degrade the CMB damping tail fit and drive the optical depth to unphysical values.
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The paper's central claim is that a single 'high-τ' prior, τ = 0.11 ± 0.006, imposed in place of the standard low-multipole CMB polarization likelihood, makes ΛCDM concordant with the full set of current distance and clustering measurements. Within this universe, the sum of neutrino masses is inferred as Σmν = 0.10^{+0.04}_{-0.05} eV (68% CL), which the authors describe as the first 2σ cosmological detection of a positive, physical neutrino mass in ΛCDM; the lensing-driven preference for 'negative' neutrino mass disappears. The same prior raises the CMB Hubble constant to H0 ≈ 68.9 km/s/Mpc, matching the galaxy-clustering value and reducing the Hubble tension to 4.4σ, and brings predicted BA
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When the scalar potential is purely quadratic (μ=0), the fractional model with dynamically evolving G and H becomes the only variant that is both statistically competitive with ΛCDM and dynamically consistent: it yields an overdamped relaxation timescale τ_rel≈9 Gyr, well-constrained fractional exponents, and late-time cosmographic functions that closely track but do not coincide with those of ΛCDM, while the full quartic model is disfavored by BIC and by parameter degeneracies.
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A minimally coupled three-form with a Gaussian potential is a viable, competitive description of the cosmic expansion history. It is mildly preferred over ΛCDM precisely for the most tensioned early-plus-late combination (CMB+DESI BAO + Pantheon+SH0ES), becomes neutral for the less-tensioned early-plus-late set, and is disfavoured or inconclusive when early-only or late-only data are used. The dynamics produce a characteristic phantom phase at intermediate redshifts while recovering cosmological-constant behaviour at early and late times.
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When a dynamical dark-energy fluid is placed in a Bianchi Type-V spacetime, the residual shear density couples to the expansion history and to linear growth in such a way that simultaneous late-time measurements of distances and structure growth are better accommodated, thereby lowering the statistical tension between local and early-universe determinations of both H0 and S8.
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In a compact seven-route covariance summary, combining the Cepheid--SN Ia route with three level-1 alternatives (TRGB, JAGB, and Mira) and three level-2 alternatives (SBF, Tully--Fisher, and SNe II) gives H0=73.30±0.92 km s^{-1} Mpc^{-1}, still 5.6σ above Planck base-ΛCDM.
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Localized FRBs supply a precise dispersion measure-redshift relation that models the intergalactic medium electron density tightly enough to deliver independent low-redshift H0 values competitive with other probes and to constrain dark energy equation-of-state parameters, while current samples already demonstrate this utility and future surveys will deliver more stringent limits on cosmic acceleration.
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Within the symmetric teleparallel framework, the logarithmic f(Q) model infers intermediate values of the Hubble constant between the Planck and SH0ES benchmarks for all combinations of cosmic chronometers, Type Ia supernovae, and BAO data, while both models remain statistically competitive with Lambda CDM and the logarithmic variant shows lower AIC and BIC values.
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Current observations do not generically exclude sterile neutrinos, but rather place strong pressure on fully thermalized or highly populated scenarios, highlighting the importance of production history and phase-space distribution when interpreting cosmological constraints.
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The energy density of the hybrid dark energy model is formed by combining the contributions from a generalized length-time cut-off, reducing to the usual holographic and new agegraphic forms in the appropriate limits. In both interacting and non-interacting scenarios with cold dark matter, the model parameters are fitted to observational data, and the resulting cosmology reproduces the observed expansion history while keeping the Hubble tension low.
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The paper establishes that the Hubble-constant discrepancy persists whether or not early constraints use Planck CMB and whether or not late measurements use a full three-rung distance ladder, and that pure early-Universe sound-horizon solutions and pure late-Universe absolute-magnitude solutions are each blocked by no-go constraints, leaving interacting dark energy (combining early and late modifications) or new physics at the inhomogeneity-to-homogeneity transition as the remaining reviewed options.
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The considered teleparallel cubic Galileon models can accommodate the late-time expansion history, although the statistical preference depends on the choice of potential and on whether b1 is fixed or varied. In particular, the fixed-b1 model with a quadratic potential provides the most competitive fit among the Galileon scenarios when BAO data are included, showing a lower χ²_min than ΛCDM and comparable support according to the AIC criterion. However, the BIC criterion continues to favor the minimal ΛCDM model because of the larger parameter space of the extended models.
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The authors state that the cosmological constant supplies a natural account of the Hubble tension by assigning different Hubble parameters to local and global flows. The repulsive Λ-effect is essential for void stability today: when Landau damping suppresses discrete collapse modes, random local density perturbations inside voids cannot grow and add galaxies to the walls. Inside the voids the Λ-repulsion dominates the attractive force of residual matter, accelerating outward migration to the boundaries. Consequently, cosmic voids in the Local Universe have entered a phase of stable and more pronounced walls, as indicated by observational surveys at varying redshifts.
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Within the canonical axion EDE framework, the CMB+DESI+JWST data significantly increase the H0 value to 71.58±1.05 km s^{-1} Mpc^{-1}, alleviating the H0 tension to the 1.0σ level. Simultaneously, this model improves the fit to the JWST data and exhibits statistical performance significantly better than the Λ CDM model, with Δχ²_tot = -18.26 and ΔDIC = -11.89.
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DESI recovers the CMB-constrained combination (r_d h)(Ω_m/0.3)^{0.4} to sub-percent precision, showing agreement between intermediate-redshift BAO and the recombination acoustic scale. When the CMB constraint is imposed, the inferred Ω_m is slightly lower than the Planck value but only mildly discrepant. High-redshift DES supernovae match the model well, while the low-redshift anchor sample shows an offset of about 0.05 mag that largely drives any apparent preference for evolving dark energy; preliminary DEBASS data lack this offset, pointing to systematics as the likely cause. The overall result is that one flat ΛCDM model suffices for the distance-redshift relation from the local universe
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The authors formulate the Λ_ωsCDM model with an additional matter-with-pressure term at early times. MCMC analysis with Planck 2018, DESI DR2, and Pantheon+SH0ES data constrains the barotropic factor to ω_s = 0.294^{+0.014}_{-0.004} and 10^5 Ω_s = 1.62^{+0.36}_{-0.56}. These parameters increase the Hubble constant to H_0 = 71.51^{+0.72}_{-0.74} km/s/Mpc, alleviating the Hubble tension while recovering ΛCDM at late times.
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Coupling H(z) and fσ8(z) through the GR linear growth equation during PINN training is both feasible and beneficial: an ensemble of 100 dual-head networks recovers either local H0 prior exactly, produces indistinguishable fσ8 reconstructions that lie below the ΛCDM+GR curve at essentially all redshifts, and yields Om(z) profiles that are not flat, while the physics weight λ = 0.1 balances data fit against ODE residual without either term dominating.
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An underdamped damped-oscillator dark-energy model yields H0 = 70.9 ± 1.1 km/s/Mpc (DESY5) and H0 = 72.0^{+1.4}_{-2.1} km/s/Mpc (Union3), reducing the SH0ES tension to ∼1.5σ, while Bayesian evidence versus ΛCDM is inconclusive; Pantheon+ instead prefers a near-critical solution with H0 = 66.23 ± 0.85 km/s/Mpc.
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The combination of DESI BAO and uncalibrated Type Ia supernovae data yields a value for H0 that is significantly higher than the ΛCDM prediction based on early-universe probes, indicating that the origin of the Hubble tension lies in new physics at low redshifts.
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Within ΛCDM the BAO–SN matter-density gap ΔΩ_m = 0.037 is exactly invariant under the sound-horizon rescaling α ≡ r_s^mod / r_s^ΛCDM, and late-time w(z) deformations cannot eliminate this gap either: reconciling the two datasets requires opposite deformations—phantom (w < −1) for BAO, quintessence (w > −1) for SN at z < 0.5—an anti-alignment quantified by cosθ = −0.97 in w(z) space.
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Using a modified RAMSES code, the authors simulate an interacting dark energy model with energy transfer rate Q equal to xi times H times rho_x. Because the dark matter Euler equation stays identical to Lambda-CDM, the interaction is carried only by the altered expansion history and a time-varying dark matter particle mass. The resulting runs show scale-dependent shifts in the quasi-linear and non-linear matter power spectrum, together with altered density-field morphology and halo abundance.
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The paper's central discovery claim is that a small out-of-equilibrium axion population — modeled by a BGK collision term whose sign is opposite to the usual relaxation term — produces an axion energy density that deviates from the standard (1+z)³ scaling at redshifts z ≲ 1, effectively acting as a phantom energy component. This modified expansion rate reconciles a high local Hubble constant with DESI BAO data. The authors derive the same macroscopic evolution for the axion density from both kinetic theory and a classical field perturbation, and the dynamics asymptotically return to ΛCDM at earlier epochs. With the SH0ES calibration included, the model is strongly preferred over ΛCDM, with H
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The central claim is that the inverse symmetron coupling produces mass-varying neutrinos whose late-time decoupling shuts down the fifth force, inhibits excessive growth of neutrino perturbations, and thereby eliminates linear-regime instabilities. The resulting model registers as a lower effective neutrino mass in galaxy surveys, adds extra suppression to the matter power spectrum, and can include an early dark energy component localized around recombination.
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Using Planck and ACT data including lensing, a perturbative modification to m_e(z) fully resolves the Hubble tension, sharing the same qualitative oscillatory structure as in previous work using Planck data alone. Once DESI DR2 BAO data are added, however, perturbative modifications to m_e(z) cannot fully resolve the Hubble tension. This reflects the fundamental limitation that raising H0 by modifying recombination generically lowers Omega_m, being inconsistent with late-time cosmological observations.
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If local distance measurements are analyzed with the w0wa models preferred by the DESI measurements, the value for the Hubble constant can be as much as 2.5 km s^{-1} Mpc^{-1} smaller than the value obtained assuming LambdaCDM. When these w0wa models are further constrained by cosmic microwave background (CMB) and type Ia supernova (SNIa) data, the downward shift is 1.1 ± 0.38 km s^{-1} Mpc^{-1} (DESI + CMB) and 0.5 ± 0.1 km s^{-1} Mpc^{-1} (DESI + CMB + SNIa). The dependence of local determinations of H0 on the background cosmology, combined with the fact that the low-redshift cosmology is not well constrained, is relevant to the Hubble tension.
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In this work, 142 gravitational-wave standard siren events from GWTC-4 are combined with the latest TDCOSMO2025 time-delay strong lensing data to constrain H0 using a cosmological-model-independent framework based on the distance sum rule. With the FullPop-4.0 population model and TDCOSMO2025-only lensing configuration, H0 is measured as 83.78^{+12.53}_{-10.23} km s^{-1} Mpc^{-1} at 13.58% relative precision. The precision depends primarily on the mass-sheet transformation treatment, and switching to the H0LiCOW method yields a tighter constraint of 75.42^{+3.74}_{-4.66} km s^{-1} Mpc^{-1} at 5.57% precision. All results remain consistent with both Planck and SH0ES values at the current leve
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On the paper's own terms, the central discovery is that the gravitational-potential difference between our location and sources at z ≳ 0.3, encoded in the dimensionless parameter z0, is constrained to z0 = −0.4+0.8−0.9% for data at z > 0.5 and z0 = 0.0+0.6−0.7% when data at z > 0.29 are included. The previously expected value of 0.84% sits within the joint uncertainty, and a model forced to z0 = 0.84% fits the combination of BBN, CMB, BAO, and CC data almost as well as ΛCDM, with Δχ² < 2. In the standard BAO parameter space, the internal ΛCDM tension between BAO and non-BAO datasets is 2.81σ; fixing z0 = 0.84% drops this to 2.39σ, which lies within the 99% credible region.
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Fitting the hybrid redshift duality model to Pantheon+SH0ES recovers the metric-expansion Hubble constant H_Λ to a value consistent with the Planck baseline of 67.4 km s^{-1} Mpc^{-1} within ≲0.33σ, while restoring constancy of H_Λ across redshift bins.
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The exponential f(R) gravity model yields H0 values slightly lower than those obtained in Lambda CDM, indicating no significant relaxation of the H0 tension. In contrast, the model predicts systematically higher values of S8, leading to a moderate alleviation of the S8 tension by up to approximately 1.2 sigma when late-time datasets are included. Overall the results show that the model does not resolve all cosmological tensions simultaneously yet provides a consistent improvement in the description of large-scale structure formation.
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Within Tsallis' statistical framework, two distinct definitions of fugacity are identified for relativistic and non-relativistic regimes. For the non-relativistic sector, an effective chemical potential is introduced and connected to the Gibbs free energy. A phenomenological correspondence is established between this effective chemical potential and an Unruh-like temperature associated with accelerated trajectories in an expanding cosmological background. This yields an effective expression for the Hubble parameter that includes a statistics-dependent contribution arising from the non-relativistic matter sector, increasing sensitivity to underlying thermostatistical assumptions by approximat
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By constructing a BBN simulator with nested sampling, the authors derive that a linear equation of state restricts dark energy density to less than 10^{-13} MeV^4 and a polytropic equation of state to less than 10^{-5} MeV^4 at 95% confidence level. A temperature-dependent equation of state remains consistent with observed primordial abundances for coupling parameters ≲ 10^{-2}, because it permits high-temperature deviations from the standard expansion history yet dilutes quickly enough to reproduce general-relativistic results before weak freeze-out.
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Satisfying the dynamical requirements for both early dark energy relevant to pre-recombination Hubble-tension solutions and late-time acceleration necessitates a scalar potential with three distinct slopes arranged in a steep-steeper-shallow hierarchy. This conclusion is unchanged by the addition of conformal couplings to dark matter.
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We investigate an extension of Lambda CDM in which a fraction of cold Dark Matter (DM) decays into invisible dark radiation (DR) around the radiation-matter equality epoch, together with a non-standard dark energy (DE) equation of state characterized by w0. The decaying DM component modifies the early expansion history and reduces the sound horizon at baryon drag, while the DE alters the expansion rate at the late times. A comprehensive analysis combining Planck 2018+ACT DR6+DESI DR2+CMB lensing datasets has been carried out to explore the viability of this framework in addressing the H0 tension. This model yields a Hubble constant of H0 = 69.83 ± 0.98 km s^{-1} Mpc^{-1}, reducing the discre
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In the high-frequency approximation on an FLRW background, the transverse-traceless tensor perturbations obey a modified wave equation whose dispersion relation includes a time-dependent effective mass m_eff fixed by the background k-essence field. This m_eff can be expressed as a function of redshift alone, m_eff(z), thereby connecting observable waveform distortions directly to the scalar-field dynamics without altering the gravitational-wave luminosity distance.
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The axion-like EDE model with potential index n=3 achieves chi-squared minima of 65.70 for Planck-EB and 48.08 for ACT-EB, with coupling values g M_pl = -0.210 plus or minus 0.024 and -0.158 plus or minus 0.025 that reproduce the observed EB spectra across angular scales, outperforming both n=2 and n to infinity while remaining theoretically consistent.
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The phenomenological dark radiation framework yields N_fld < 0.66 (95% C.L.) from CMB alone and, with BAO, N_fs = 2.93 ± 0.23 and N_fld = 0.36^{+0.16}_{-0.21} (68% C.L.). The same data combination reduces the sound horizon to r_d = 141.8^{+1.3}_{-1.2} Mpc and lifts the Hubble constant enough that the tension with SH0ES becomes statistically non-significant according to the T-statistic. Adding SH0ES produces decisive Bayesian evidence for the dark radiation scenario, with total effective radiation N_tot = 3.63^{+0.13}_{-0.15} and free-streaming fraction f_fs = 0.392 ± 0.026 when Pantheon+ is also included.
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The QDEE model adds two extra parameters that allow the dark energy density to deviate quadratically from a constant at late times. Constraints from Planck 2018, ACT DR6, SPT-3G, DESI DR2, and Pantheon Plus data shift the posterior for the Hubble constant upward while preserving consistency with early-universe observables. Bayesian model comparison yields strong evidence in favor of QDEE, and posterior predictive checks confirm that the model's predictions remain statistically compatible with the observations.
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In unimodular gravity, the addition of spatial curvature together with a diffusion term of the form Q(z) = Q0(1+z)^β that obeys the second law produces a higher present-day Hubble rate H0 = 73.35 km/s/Mpc, a closed-universe density parameter Ωk0 ≈ -0.11, and an effective dark-energy equation of state ωeff ≈ -0.83, all while the cosmic age remains t0 ≃ 13.61 Gyr and the sound horizon is left unchanged.
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In this scalar-vector-tensor theory, the conformal scalar coupling modifies the physical expansion rate measured by matter observers, leading to a late-time enhancement of the effective Hubble constant. By constructing a phenomenological scalar evolution that becomes relevant only at low redshifts, the model provides a purely late-time mechanism for alleviating the Hubble tension without significantly affecting early-universe cosmology. The scalar potential naturally acts as a dynamical dark-energy sector, while the vector contribution behaves effectively as a pressureless component at cosmological scales through a density-dependent vector mass.
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Within a common flat-ΛCDM framework, each probe posterior is mapped onto posterior-implied E(z) histories. The reconstructed values E(z_k) are strongly correlated across redshift, so the global mismatch is quantified with a covariance-subspace history displacement S_hist, alongside pointwise redshift differences. The histories are not identical, but the discrepancies are moderate: the pointwise significance is typically 1-2σ, while S_hist ≃ 1.65 for DESI DR2 and S_hist ≃ 2.55 for Pantheon+SH0ES relative to Planck. With two retained covariance eigenmodes, these correspond to two-sided one-dimensional Gaussian equivalents of approximately 1.1σ and 2.1σ, both below the conventional ≃ 4.9σ 0.1σ.
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Using multiple parameterizations for possible violations and fitting to observational data, the study finds no significant departure from the cosmic distance duality relation. Model selection favors flat scenarios even though slight curvature is not ruled out entirely. Supernovae data without DESI prefer a higher Hubble constant while Planck combined with DESI and gamma-ray bursts prefer a lower value.
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The emergence of Big Bang 2.0 reflects the profound paradigm shift from a model based on standard physics to a dynamical cosmos dominated by dark matter and dark energy, the description of which requires a physics that has yet to be developed and validated.
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The ΛsCDM model, defined by the interaction term Q = ξ H ρ_de together with a dynamically induced effective pressure in the dark matter fluid, yields H0 = 71.8_{-0.3}^{+0.4} km s^{-1} Mpc^{-1} when constrained by Planck 2018 CMB, DESI DR2 BAO, Pantheon+ supernovae, Hubble data, and RSD measurements. This value reduces the tension with the SH0ES local Hubble measurement from about 5σ in ΛCDM to 1.2σ while leaving the pre-recombination sound horizon within 1% of its ΛCDM value and producing σ8 = 0.744 ± 0.0185.
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Synthesizing existing analyses shows that while power-law, exponential, and logarithmic f(Q) models can alleviate the H0 tension or the S8 tension individually, the simultaneous requirement of consistency with the growth index or fσ8(z) shape restricts the allowed parameter space severely. The same filtering occurs when a bulk-viscous component is introduced. Only a restricted subset of f(Q) models therefore remains competitive under the global consistency requirement.
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Translating the bounds from unitarity, positivity, NA64μ, and global fits onto the effective four-neutrino coupling G_eff yields values many orders of magnitude smaller than the strongly interacting regime motivated by the Hubble tension. This excludes heavy-mediator UV completions of strong ν_μ–ν_μ and ν_μ–ν_τ self-interactions within the validity of the dimension-six SMEFT and in the absence of tuned cancellations between operators, while leaving cosmologically motivated light-mediator scenarios unconstrained.
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Confronting an extended cosmological model that includes self-interacting dark radiation together with running α_s and running of the running β_s of the spectral index against Planck, ACT DR6, DESI DR2, and uncalibrated Pantheon+ data yields a relaxed upper bound ΔN_eff < 0.58 at 95% CL, a 2.9σ preference for α_s > 0, and reduces the Hubble tension to 2.2σ. In the variant where dark radiation decouples from dark matter near matter-radiation equality, the bound becomes ΔN_eff < 0.68 and the tension drops below 2σ.
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In order to have a reliable measurement of the Hubble constant at the level required to resolve the Hubble tension in the future, the mass distribution of the BBHs needs to be independently inferred at all relevant redshifts with an accuracy less than the statistical uncertainty. Otherwise, a mismatch of the true model and the underlying assumption made in the analysis can lead to a best-fit model for the wrong value of both BBH population parameters as well as the Hubble constant. The blinded mock data challenge analysis demonstrates the criticality in capturing the underlying metallicity dependence of the BBH mass distribution and its interplay with time-delay distribution for a robust use
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A model-independent reconstruction of the background pre-recombination expansion history demonstrates that purely early-time resolutions to the Hubble tension exist at the background level. These solutions require a smooth transition around matter-radiation equality characterized by a roughly 15% expansion rate enhancement prior to recombination.
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We review a new natural inflationary mechanism operated by repulsive-like primordial black holes. In particular, working within the Swiss-cheese cosmological framework, we find that a Universe filled with PBHs, whose spacetime metric presents a repulsive-like behaviour, is characterised by an early quasi-de-Sitter cosmic expansion phase. Notably, for light PBHs with m < 5 × 10^8 g, evaporating before Big Bang Nucleosynthesis (BBN), one is met with an exponential inflationary phase with graceful exit and reheating proceeding through PBH evaporation. Furthermore, one finds as well that PBHs with m ∼ 10^12 g and abundances 0.107 < Ω^eq_PBH < 0.5 near matter-radiation equality can act as anearly
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We find no evidence for a redshift-dependent calibration effect when fitting uncalibrated SNIa data, and its inclusion has a negligible impact on cosmological parameters within Lambda CDM. When incorporating a prior on the SNIa absolute magnitude from SH0ES, a nonzero calibration parameter is weakly preferred within Lambda CDM. With dynamical dark energy, the preference of a nonzero calibration parameter increases to 4.3 sigma, and it can accommodate both the distance ladder and early-Universe constraints, reducing the Hubble tension to 1.5 sigma, with the best-fit model effectively corresponding to a constant equation of state with w less than negative one.
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Artificial neural networks are trained to reconstruct the necessary distance functions directly from the data. These reconstructions are then combined via the distance duality relation across DESI DR2 baryon acoustic oscillations, supernovae, and cosmic chronometers to produce a model-independent Hubble constant of 71.5 plus or minus 2.2 km s^{-1} Mpc^{-1} at 68 percent . The value is consistent with local measurements within 0.6 sigma and with Planck within 2 sigma, thereby favoring a higher H0.
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The central finding is that relative uncertainties of 10 percent or less on the primordial black hole parameters M_PBH and f_PBH translate into an uncertainty on H0 of at most 2 km s^{-1} Mpc^{-1} in a conservative multi-band analysis, improving to order 0.1 km s^{-1} Mpc^{-1} in an optimistic precision case, with the results largely insensitive to the fiducial H0 value and only moderately dependent on collapse efficiency.
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For scale-free power spectra in an Einstein-de Sitter cosmology, the halo mass function is not universal but depends explicitly on the slope of the input power spectrum. An effective index drawn from the Lambda CDM power spectrum can therefore reproduce the scale-free halo mass function as a first approximation. Structure formation drives deviations from homogeneity and isotropy out to at least 100 Mpc/h, which produce errors in Hubble constant estimates that correlate with the local density around the observer. Mock observations show deviations reaching 5 percent in Milky Way-sized halos, indicating that this local effect may explain part of the Hubble tension. Missing small-scale power in
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The central discovery is that a barotropic fluid obeying P = ω_s ρ with ω_s > 0 modifies the pre-recombination expansion history in a way that reconciles the CMB-inferred Hubble constant with direct local measurements, without violating late-time constraints on structure formation or the expansion rate.
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Starting from the Gibbs relation for pressureless matter, the analysis derives a thermodynamic admissibility condition that forces dot Q less than zero for the second law to hold. This condition directly precludes the positive time derivative of the effective cosmological term that the referenced models require to address the Hubble tension. The incompatibility is independent of the specific functional form of Q(t) and applies uniformly to the Lambda CDM plus diffusion models in unimodular gravity.
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When the six-parameter multi-domain backreaction model is constrained solely by PantheonPlus+SH0ES data, the derived optical depth to reionization is τ_reion = 0.0581^{+0.0105}_{-0.0096} (68 % CL), which agrees better with Planck and other observational determinations than the corresponding ΛCDM prediction from the same supernova sample, while the inferred H_0 simultaneously moves closer to the early-universe value.
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We show that the strong constraints placed by Planck NPIPE Cosmic Microwave Background (CMB) data on axion-like early dark energy (EDE) are significantly alleviated in models with multiple fields. We find a 1.5 sigma residual tension with the Local Distance Network value of H0 in a 2-field model, with no improvement beyond two fields, and a best-fit value of H0 ~1.4 sigma larger than in the 1-field case. The second field improves the fit to high-ℓ CMB data, where 1-field EDE is most strongly disfavored, and suggests modifications to the pre-recombination history over a wider redshift range.
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The published 3D BAO distances are fiducial-independent by construction with residuals at the 0.3 percent level. No model in the CPL parameter space that is consistent with Planck theta-star and fits DESI well can also accommodate the BAOtr data; the reverse also fails. The direct 3.7-sigma data-versus-data disagreement at z=0.510 cannot be removed by any smooth modification of D_M(z). These results remain stable when SDSS data replace DESI and across analysis choices.
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By adopting a polytropic equation of state with free parameters in a power-law f(Q) cosmological framework, exact solutions for the scale factor and other quantities are obtained. Rigorous Bayesian parameter estimation from data then yields constraints on the model parameters, allowing interpretation of the deceleration parameter and statefinder diagnostics. The model thereby provides a specific prediction for the current value of H0 and its implications for the observed tension between early- and late-time measurements.
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The BAO and SN sides of the tension can be treated independently. Early dark energy reduces the CMB-BAO tension by changing the calibration of the sound horizon at the drag epoch rd, with a Delta chi squared of -9.4 relative to Lambda CDM and raising H0 to 70.87 km s^-1 Mpc^-1. Combining this with a thawing-quintessence component of dark energy reduces tensions between CMB, BAO, and SN data with Delta chi squared of -12.6 without a phantom component, compared to -15.8 for w0wa with one, while reducing the Hubble tension with local measurements from 7 sigma to 2-3 sigma.